i965: Move env_var_as_boolean to intel_debug.c.

I need to use this in brw_vec4.cpp, so it can't be static anymore.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/mesa/drivers/dri/i965/intel_debug.c

@@ -106,3 +106,28 @@ brw_process_intel_debug_variable(struct brw_context *brw)
    if (INTEL_DEBUG & DEBUG_AUB)
       drm_intel_bufmgr_gem_set_aub_dump(brw->bufmgr, true);
 }
+
+/**
+ * Reads an environment variable and interprets its value as a boolean.
+ *
+ * Recognizes 0/false/no and 1/true/yes.  Other values result in the default value.
+ */
+bool
+brw_env_var_as_boolean(const char *var_name, bool default_value)
+{
+   const char *str = getenv(var_name);
+   if (str == NULL)
+      return default_value;
+
+   if (strcmp(str, "1") == 0 ||
+       strcasecmp(str, "true") == 0 ||
+       strcasecmp(str, "yes") == 0) {
+      return true;
+   } else if (strcmp(str, "0") == 0 ||
+              strcasecmp(str, "false") == 0 ||
+              strcasecmp(str, "no") == 0) {
+      return false;
+   } else {
+      return default_value;
+   }
+}